So the title says it, but I'll clarify if it's unclear. I'm trying to find a way to reduce the amount of dust taken in by my new bottom intake PSU fan. Right now it's over a rug, which I know is full of dust (because carpets get dusty, not because I don't clean) I'm worried about a dust filter reducing airflow, so I'm a little reticent to do that, though that may be the option to use.

I thought about putting it on a hard surface to reduce the amount of dust, but that feels like I'm not going to do much other than slow the process.

dont put your pc on carpet or like that coz they would catch dust faster
and air filter would reduce airflow, just little bit but it would be ok
dust on heatsink would reduce heat escape too, i prefer using air filter

1) Vacuum the carpets
2) Put the computer on top of something, direct contact with a dusty rug is asking for a dead psu in six months
3) Use a humidifier next to the intake
4) Put a dust filter on, they're like $15 online(link)

I have a carpeted apt and put my rather large PC tower on the floor beside my desk, but I place it on an oak veneer shelf board that came with a rail wall mounting kit. The board is 8"x24"x3/4" and is the perfect size for it. It's got some coats of clear polyurethane on it, and vaguely matches the color of my carpet.

I also have a small air filter which I run daily for half an hour to an hour, mainly to use the ionizer on it. An ionizer negatively charges the air particles, and then causes particles in the air to settle to the floor. Effectiveness and duration depends on size of room, but don't leave one on too long, they can start to create an artificial "smog" effect.

My Antec DF-85 case doesn't have bottom vents though. Antec tends to stay away from that design, preferring less dusty front to back airflow. You could however block your bottom vents and/or invert your PSU, but that would also increase negative air pressure, which can also suck in dust.

I would advise just trying the board underneath for now and maybe add as many intake fans as you can. BTW, my case is filtered on all intakes and still has quite good airflow. Not all cases are created equal in this regard.

Oh good lord... dust filters. It should be mandatory that all cases come with them. I'm forever cleaning out friends and client cases of caked up dust because they have no filters. I clean mine once a month, and the inside of my case is nearly pristine. They can't get everything of course, but it's a giant help.

My computer tower sits directly on a maple floor in my room. its like 4 years old now and has been in alot of carpeted houses since I had it. it does get some dust but thats expected. we have 2 dogs and a cat that comes around.

If you Have a Flooring Store, or a Home Depot, or lowes , around where you live , you Could buy a Single plank of Laminate Wood flooring , Like pergo , or the like. That would be Easy to cut if needed and it Would be the same as the PC sitting on a Hardwood floor, as far as the underneath is concerned. It work's Fine, I've done it before. Plus it would last forever.They are about the Width of a Standard Mid tower anyway , so you would just need to Stick it under there. Good Luck. Also the pantyhose Idea is a Viable solution as well , when your in a pinch.

I think you shouldn't worry that much. After all you don't live in a sawmill, it's a regular apartment. Regardless of whether you have possitve or negatvie with intake holes pressure, e.g there is at least one fan moving the air inside the case, the dust won't settle.
I just realized, you said bottom mounted PSU, so it doesn't really take part in the cooling process. May be flip it, so that it sucks air from the inside of the case>? Or most probably leave it like that and clean it every 6 months or so carefully.